Fire-retardant finish for nylon

ABSTRACT

A composition for imparting fire retardancy to nylon textiles, comprising highly methylolated urea, thiourea and ammonium chloride; the method of imparting fire retardancy to nylon textiles; and a nylon textile having fire-retardant properties.

United States Patent Busch, Jr.

[ 5] Feb.l,l972

[54] FIRE-RETARDANT FINISH FOR NYLON [21] Appl. No.: 723,951

[52] U.S. Cl ..252/8.l, 106/15 FP, 117/137, 1 17/1383 N [51] Int. Cl,.C09d 5/18, C09k 3/28, B32b 27/08 [58] FieldolSearch ..l17/l38.8 N,136, 137; 260/294; 106/15 FP; 252/8.1

[56] References Cited UNITED STATES PATENTS 2,415,112 2/1947 Seymouretal..ll7/l37 2,466,457 4/1949 Lynnetal ..|l7/l4l 2,795,513 6/1957 Rossin..l 17/138.8 X 2,922,726 1/1960 Moretti et 111.. ....1 17/1388 X3,317,345 5/1967 Fluck el al..... ..l l7/l38.5 3,335,113 8/1967 Dundon..l 17/1395 X Primary Examiner-William D. Martin Assismn! Examiner-Marry.l. Gwinnell Attorney-Charles Joseph Fickey [5 7] ABSTRACT A compositionfor imparting fire remrdancy to nylon textiles, comprising highlymethylolated urea, thiourea and ammonium chloride; the method ofimparting fire retardancy to nylon textiles; and a nylon textile havingfire-retardant properties.

3 Claims, No Drawings FlRE-RETARDANT FINISH FOR NYLON This inventionrelates to a fire-retardant finish for nylon textile materials. Moreparticularly, it relates to (I) a fire-retardant finish comprisinghighly methylolated urea, thiourea and ammonium chloride, (2) the methodof applying the finish to nylon textile materials and (3) to be treatednylon materials.

The importance of imparting fire-retardant properties to nylon textilematerials is well known. Textile fabrics have been treated with a widevariety of thermosetting resins to produce a diversity of resin finisheson the cloth. Among the many objects have been resistance to shrinking,resistance to wrinkling, the stiffening of limp fabrics and reducing thecombustibility of the material. The commoner varieties of textile resinsinclude water-soluble condensation products of formaldehyde with urea ormelamine and the ethers obtained by treating the aforesaid condensationproducts with methanol. Water-soluble unalkylated thiourea-formaldehyderesins have also been proposed for flameproofing nylon. As might beexpected, the resin finishes used to produce or improve one desirableeffect on a textile fabric occasionally have an undesirable effect onother qualities of the material. In addition, the various resins havepeculiarities which in one manner or another limit their use.

In spite of the many patents on fire-retardant finishes for nylon, theneed is still present for an economical, easily applied, and effectivefire-retardant finish for textile materials containing a principalamount of nylon fibers.

It is therefore an object to provide a composition and process forimparting flame rctardance to nylon textiles.

It is a further object to provide a flame-retardant finish for nylontextiles which is economical, easily applied, and highly effective.

Another object is to provide a flameproof nylon textile.

These and other objects of my invention will become apparent as thedescription thereof proceeds.

Such a finish has now been discovered which meets the abme requirements.The finish of the present invention comprises an aqueous solution ofhighly methylolated urea, thiourea. and ammonium chloride.

The methylolated urea contains at least 3.0 moles of combinedformaldehyde, preferably at least 3.3 moles, per mole of urea. Thepreparation of the highly methylolated urea is described in U.S. Pat No.3,335,l l3, and is as follows:

The process for preparing a water-soluble stable urea formaldehydecondensation product comprises reacting relative amounts of l mol ofurea with from between 4 and 5 mols of formaldehyde at a pH above and inthe presence of an amount of alkali that does not exceed 0.l mol ofsodium hydroxide per mol of urea and at a temperature of between 40 and100 C. This reaction is carried out until the mols of combinedformaldehyde per mol of urea are from about 3.4 to about 3.8 and theformaldehyde content of the reaction mixture is below 4 percent.

In preparing the highly methylolated urea composition, relative amountsof 1 mol of urea are reacted with between 4 and 5 mols offormaldehydeand preferably with from between from about 4.2 and about 4.6 mols offormaldehyde. Amounts of formaldehyde in excess of 4.6 mols areunadvisable because of the resulting large amounts of unreactedformaldehyde remaining in the composition.

The reaction is preferably carried out in water as a solvent, and theformaldehyde may be used as the commercial 37 percent or 44 percentformaldehyde solutions or as paraformaldehyde.

The principal reaction between urea and formaldehyde in an aqueousmedium is carried out at a pH above l0 and in the presence of an amountof alkali that does not exceed the equivalent of 0.] mol of sodiumhydroxide per mol of urea. As examples of strong alkalis, sodiumhydroxide, potassium hydroxide, lithium hydroxide, and suitable alkalineearth metal hydroxides, such as barium hydroxide, may be cited. Thesealkaline materials or their equivalents are employed in amounts that areequivalent to an alkalinity of about pH l0 and above, but should not beemployed in an amount that exceeds 0.] mol of sodium hydroxide or itsequivalent per mol of urea. At pHs appreciable below 10, the rate ofreaction between urea and formaldehyde is slow and the desired degree ofmethylolation to be discussed more fully hereinafter is not obtainable.In addition, because of the well-known Canizzaros reaction; that is, thereaction between sodium hydroxide and formaldehyde, in which causticsoda is consumed and sodium formate is formed, it is necessary to add tothe caustic soda throughout the reaction period in order to maintain thepH at a value of at least l0, while employing the caustic soda or itsequivalent in an amount not exceeding 0.l mol of sodium hydroxide or itsequivalent per mol of urea. It should be noted that if amounts ofcaustic soda or its equivalent signifcantly in excess of0.l mol per molof urea are employed in the preparation of a highly methylolated urea,undesirably large amounts of sodium formate are found to be present inthe finished product which interfere with the textile-finishingproperties of the resulting product. The sodium formate appears tobuffer the acidic catalyst normally employed to cure aminoplasts by thetextile-finishing industry.

The reaction between urea and formaldehyde is carried out until the molsof combined formaldehyde per mol of urea ratio is at least 3.4:l andpreferably is a value of between 3.6 and 3.8: l as determined byanalyses of unreacted formaldehyde.

In the carrying out of the process it has been found convenient to carryout the reaction in two stages. In the first stage urea and formaldehydeare reacted until the amount of free formaldehyde constitutes from 4 toabout 8 percent of the reaction mixture while this excess freeformaldehyde may be removed by distillation, in accordance with theimportant and preferred aspect of this invention the pH of the reactionmixture is adjusted to a value of below 8.5 but above 7 and urea in anamount of from between 0.2 mol and 1 mol per mol of initial urea isadded to the reaction mixture. Methylolation of the additional urea isthen carried out until the unreacted or free formaldehyde content of thereaction mixture is less than 4 percent and preferably less than 3percent by weight of the reaction mixture.

lfthe pH is not adjusted to a value ofbelow 8.5 but above 7, prior tothe second addition of urea, undesirable side reactions occur whichappear to result in the formation of polymeric materials which aredetrimental to the stability of the final product. As indicated abovethe amount of additional urea is from about 0.2 to about I mol relativeto the initial mol of urea but is added in an amount sufficient toreduce the free formaldehyde content to a value of less than 4 percentand preferably less than 3 percent based on the total weight of thereaction mixture,

In accordance with the process. the methylolation is carried out at atemperature of from between 40 and I00 C. and preferably at atemperature from between 60 and C. In accordance with theabove-described two-stage methylolation in which the pH is adjusteddownwardly prior to the second addition of urea, this adjustment can beconveniently accomplished in accordance with the present invention byraising the temperature of the reaction mixture to a value of about C.,which accelerates the Cannizzaro reaction between the formaldehyde andcaustic soda resulting in a lowering of the pH to a value of between 7and about 8.5.

Typical compositions of methylated urea products may be characterized ascontaining l mol ofa polymethylol urea, having between 3.6 and 3.8 molsof combined formaldehyde, about 0.l to about 0.3 percent of dimethylolurea and about 0.2 to about 0.4 mols offree formaldehyde.

A typical final methylated urea product may be characterized ascontaining l mol of a polymethylol urea having between 3.6 and 3.8 molsof combined formaldehyde. about 0.2 mols of dimethylol urea and about0.3 mols of free formaldehyde plus water and minor amounts of dissolvedsalts.

The typical products will be water-white liquids having a pH of between7 and 8.5. As stated above, the formaldehyde should be less than 4percent and preferably less than 3 percent of the weight of the product.

The amount of highly methylolated urea applied to the fabric should bebetween 1 percent and I percent, preferably between 3 percent and [0percent, based on the weight of the fabric (o.w.f. J. The amount ofthiourea should be between 0.5 percent and percent o.w.f., preferablybetween 1 percent and 8 percent o.w.f. The amount of ammonium chlorideshould be between 0.035 percent and 0.55 percent o.w.f., preferablybetween 0.10 percent and 0.35 percent o.w.f.

The aqueous finish is applied to the nylon material by standardprocedures such as by padding, dipping, spraying. etc.

After the nylon is dried (for example in an air dryer at 225 F. i, it isheated at an elevated temperature. A temperature between 300 F. and 375F., preferably between 325 F. and 350 F., is normally used. The heatingperiod is of sufficient duration to essentially insolubilize the ureaand thiourea components on the fabric.

The nylon textile materials may contain other fibers, both natural andsynthetic, such as silk, cotton, wool, viscose, Dacron, Orlon, acetate,etc., but will comprise at least 80 percent nylon. The textile materialsmay be fibers, threads, woven or knit fabrics, or nonwoven materials,etc.

The following specific examples are provided to illustrate the inventionand are not intended to be limitative.

EXAMPLEI Two pad baths were prepared of the composition shown in tableI.

Resin Amethylolated urea containing 2.8 moles of combined formaldehyde.

Resin B-methylolated urea containing 3.5 moles of com binedformaldehyde.

Table l Pad Balh l 2 Re in A l3 U' i Resin B lllli Thlourea (i 5 6.5

Ammonium Chloride (l 45 0.45

The above pad baths were applied to swatches of 5-ounce, white nylonfilament (tarpaulin) fabric by a padding procedure using two dips andtwo nips at 2 tons pressure. The wet pickup was 31 percent. The treatedfabrics contained the percentage amounts of active ingredients shown intable 2. The fabrics were dried at 225 F. and then heated at 350 F. forL5 minutes.

Fire retardancies ofthe treated fabrics were tested by holding a flamefor 12 seconds at the lower edge of swatches of each fabric heldvertically. The results are shown in table 2. Fabrics l and 2 correspondto pad baths 1 and 2, respectively.

After Flame l sec For comparison, a swatch of the untreated nylon fabricmelted.

This example demonstrates the effectiveness of the finish of thisinvention. It also demonstrates the superior fire-retardant propertiesimparted by a finish containing a methylolated urea having more than 3.0moles of combined formaldehyde per mole of urea as compared with afinish containing a methylolated urea having less than 3.0 moles ofcombined formaldehyde per mole of urea.

While certain specific embodiments and preferred modes of practice ofthe invention have been set forth, it will be understood that this issolely for the purpose of illustration, and that various changes andmodifications may be made in the invention without departing from thespirit of the disclosure or the scope ofthe appended claims.

lclaim:

l. A fire-retardant composition for nylon containing textiles consistingessentially of an aqueous solution of methylolated urea, having at least3.5 moles of combined formaldehyde per mol of urea, thiourea, andammonium chloride, present in sufficient quantities to deposit by weightof said textile on said textile: from about l to 15 percent ofmethylolated urea; from about 0.5 to 15 percent of thiourea; and fromabout 0.035 to 0.55 percent by weight of ammonium chloride.

2. The composition of claim 1 wherein the amount of methylolated urea isfrom about 3 to l0 percent; said thiourea is from about I to 8 percent;and said ammonium chloride is from about 0. 10 to 0.35 percent.

3. A nylon textile material having a fire retardant finish thereon,comprising a deposit by weight of from about I to l5 percent ofmethylolated urea, having at least 3.5 mols of combined formaldehyde permol ofurea', from about 0.5 to 15 percent of thiourea; and from about0.035 to 0.55 percent by weight of ammonium chloride.

2. The composition of claim 1 wherein the amount of methylolated urea isfrom about 3 to 10 percent; said thiourea is from about 1 to 8 percent;and said ammonium chloride is from about 0.10 to 0.35 percent.
 3. Anylon textile material having a fire retardant finish thereon,comprising a deposit by weight of from about 1 to 15 percent ofmethylolated urea, having at least 3.5 mols of combined formaldehyde permol of urea; from about 0.5 to 15 percent of thiourea; and from about0.035 to 0.55 percent by weight of ammonium chloride.